Cold Stove, Wood Smoke Leaking into Home
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An air to air heat exchanger putting slight positive pressure into the room may be more effective.
Our primary heating system is a mini-split heat pump. Is that what you mean by air-to-air heat exchanger?
The largest mini-split vent is not far from the stove. Is there a setting we might use that would help reduce the back pressure? Right now, it's just pumping heat into the room.
sneefy
Burning Hunk
Is that an intake or exhaust fan?
Lots of potential sources of negative pressure. Wind can create negative pressure in drafty homes. Wind over exhaust vents (bathrooms, range hood, etc) that don't have flappers pulling air out. Any source of combustion (traditional water heater) that doesn't have a dedicated air intake. Anything that mechanically exhausts air (yes, a dryer certainly does). Multiples of the happening simultaneously are additive.
I've always assumed it's an exhaust fan. But that's just an assumption on my part. We bought the house from a bank. It was foreclosed from the previous owner so there was no one to explain anything. It has a timer. It can be set to run continuously or according to a preset schedule. Or it can be turned off. We've always left it off. I assume it's there because modern homes are very airtight and so it's probably recommended to run it a certain number of hours per day to get rid of any toxins that might build up. That's just my assumption. I really know nothing about construction or building codes.
The point is that cold air can sink into a flue, stand there, and press out at seams or air inlets of the stove.
This is exacerbated by negative pressure in the home.
Using an ERV (Google that) set sonit creates a slight overpressure, while minimizing energy loss may help. Especially in a tight home where air quality might benefit anyway from some fresh air.
This is exacerbated by negative pressure in the home.
Using an ERV (Google that) set sonit creates a slight overpressure, while minimizing energy loss may help. Especially in a tight home where air quality might benefit anyway from some fresh air.
Was just reading up on it. Looks like for this climate, it would be a heat recovery ventilator (HRV). I'm wondering if that might be overkill. When not running the stove, I could just crack open the window behind it a tiny bit and see if that suffices to prevent back pressure. Heck, I could just put a vent in the wall which could maybe be opened and closed depending on need. Am I off base?
No, you're not.
The potential problem is that the cold air stacked in your flue creates a pressure that's larger than that in your room, even if your room is equilibrated with the outside by an open window. That would then still result in smelly leakage from your flue into your room - that you might not smell because it gets diluted due to the air exchanges thru the open window.
Having a very slight over pressure with an ERV or HRV would avoid that (air would leak into the flue rather than our).
The potential problem is that the cold air stacked in your flue creates a pressure that's larger than that in your room, even if your room is equilibrated with the outside by an open window. That would then still result in smelly leakage from your flue into your room - that you might not smell because it gets diluted due to the air exchanges thru the open window.
Having a very slight over pressure with an ERV or HRV would avoid that (air would leak into the flue rather than our).
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I can get that smoky flue smell in summer here in NJ when it's hot and damp outside. The cold masonry holds cold damp air that drops down and thru the air channels in my woodstove which does not have an OAK. It's not that bad though and doesn't happen that often.
It never happens in winter.
It never happens in winter.
Not the mini., that should have no effect because it just recirculates heated air in the room. An HRV or ERV is an independent system. This came up several years ago with the Ashford.
Does the stove have an outside air connection already?
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The stove has a cold air intake hooked up. I was thinking maybe I could place a second vent in the wall to let in just a bit of air so that air wouldn't get pushed down the chimney. But Stovekiller is saying I might an HRV or ERV to overpressure the room slightly (if I'm understanding correctly).Not the mini., that should have no effect because it just recirculates heated air in the room. An HRV or ERV is an independent system. This came up several years ago with the Ashford.
Does the stove have an outside air connection already?
That seems like a really expensive way to go. Would require a whole new machine, one that results in some heat loss, and someone to install it. I'm not sure where it would go. There's no attic and no place for ducting. So I guess it would have to be mounted right on an exterior wall.
I'm wondering if anyone has a sense of what it would cost to install an HRV. Presumably it needs to be wired into the wall. Does it need a dedicated circuit?
Leaving a window ajar will lose heat, but it would be ok as a test. So would a second vent in the wall. An HRV preheats the incoming air with the outgoing air to minimize heat loss. It could help improve the indoor air quality.
Not specifically, there are a lot of variables. The basic units cost $600-$1500 but the labor, installation, and setup costs are unknown.
Makes sense. I'll test it in a number of ways. Opening windows when we're running fans. Cracking the window behind the stove if it smells even when we're not running anything. I'll return to ask more questions if necessary. Thanks so much for all your help. Everyone else too.
PaulBunyun
Member
Sounds like you have a reverse draft. As the fire dies and stove cools you get negative pressure and air coming in through the flue. Not uncommon and isn't really an issue. The only point I would make is you should always have a CO alarm in the same room as your stove. It's always better to be safe.
Wondering, if the stove is cold can you stuff plastic bags into the bottom of the stove top to seal it off?
Or lengthen the stove pipe?
Or lengthen the stove pipe?
Thanks. We have CO2 monitors. Several of them. Three on the ground floor and two upstairs.
The problem isn't as the stove cools. It's when it's cold.
We recently shortened the pipe. When the last stove it had been lengthened to the point where it really couldn't be serviced. It has plenty of draw when it's burning. Almost too much. So I don't think lengthening is the solution.
When you speak of stuffing plastic bags into the bottom of the stove, where would you place them? I think the smell is coming from the stove pipe anyway. Even if one could seal off the stove baffles, I don't think it would accomplish anything. Maybe I'm wrong but sealing off the cold air intake from outside the house made the smell worse.
Do you have a telescopic stove pipe section? If you do it would be interesting to lift it up off the stove collar and slide an ice cream pail/or similar (trash bag) under it and lower it back down. Pipe would be much more sealed off (temporarily). Might be another easy experiment.
Earlier I had suggested sealing off the (oak) to isolate that line. That apparently made the smell worse.
I had also posted that you need to unseal that line when done experimenting. Guessing you have done that.
I have access to the bottom of the exhaust pipe on my Woodstock Fireview by lifting the top lid. There the 90 on the back is in full view so that I can seal it off with a big wad of plastic grocery bags.
It might be an experiment worth conducting. If you have access to the bottom of the chimney as it leaves the stove you can try sealing it off and see if that helps.
The trouble with telescoping the pipe is it scratches the paint. Then when I touch it up, it outgasses the first few burns. My wife hates that. We'll experiment with paying attention to the running of fans and the dryer, and maybe cracking open the window behind the stove just a bit.
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